Metering pump

ABSTRACT

RECIPROCATING PISTON PUMP ACTUATED BY A SCREW FEED AND HAVING READILY INTERCHANGEABLE PISTON AND CYLINDER ASSEMBLIES, IN ONE EMBODIMENT, A PISTON POSITION INDICATOR IS PROVIDED.

F. L. MIDDLEBUSHER EVAL METERING PUMP Filed Aug. 8, 1968 INVENTOR. PAULL. MIDDLEBUSHER WILLIAM R. BUCK N .EL ML e; TS mw E Q J rl] Si f mT\ mNN WWU unmnmnill||||||||| Jan. 19, 1971 United States Patent Office3,556,679 Patented Jan. 19, 1971 U.S. Cl. 417-63 3 Claims ABSTRACT OFTHE DISCLOSURE Reciprocating piston pump actuated by a screw feed andhaving readily interchangeable piston and cylinder assemblies; in oneembodiment, a piston position indicator is provided.

This invention relates to a reciprocating positive displacement pumpespecially suitable for accurately metering uids at a constant rate,which rate is readily capable of being changed over a Iwide range.

One of the advantages of the pump described herein is that its outputrate can be readily varied over a `Wide range. Another advantage is thatit is capable of accurate metering. In its double-acting embodiment itproduces a continuous output. Yet another advantage is that it canhandle fluids of a Wide range of viscosities, including suspensions.Still another advantage resides in the fact that its wetted parts can beconstructed from a wide variety of materials, and thus it can be maderesistant to a broad spectrum of corrosive fluids. A further advantageincludes, in one embodiment, a simple indication of iluid output volume.1

Other aspects, objects, and advantages of the invention will becomeapparent upon study of this specification, the appended claims, and theaccompanying drawing, in which:

FIG. 1 is a view, partially in vertical longitudinal section, partiallyin elevation, and partially broken away, of a preferred embodiment ofthe invention.

FIG. 2 comprises a schematic electrical diagram suitable for operationof the pump of FIG. l.

The pump as shown in the drawing comprises a base plate 10, a left endplate 11, a right end plate 12, a cover plate 13, a rear plate 14, and afront plate, removed for clarity, which serves as the near wall boundedby plates 10, 11, 12 and 13; parts 10-14 and the front plate togetherconstitute the pump casing. Secured to the eX- terior of each end plate11 and 12, as by studs, not shown, is a ange 15, to which in turn isfastened a cylinder wall 16 closed at its opposite end by a plug 17.Each cylinder wall is provided with a iluid passage communicating at itsoutward interior, such as a nipple 18, Parts 15-18 together constitute acylinder assembly, the right cylinder assembly being partially brokenaway in the drawing.

Within the pump casing is a driver assembly indicated generally as 19which comprises a hollow cylindrical block having an internal threadedbore 20, a driven spur gear 21, a drive spur gear 22, and at each end achamfer 23 serving as a bearing race. Driver assembly 19 is mountedrotatably in the pump casing by a series of bearings 24 at each of itstwo ends, which bearings in turn are seated in outer bearing races 25fastened to the interior surface of end plates 11 and 12. Threadedthrough bore 20, and passing through appropriate openings in end plates11 and 12, is a threaded piston rod 26 provided with a longitudinal keyslot 27 and, at each of its ends, a dovetail 28. A pair of pistons 29are fitted at their mating dovetail grooves 30 on dovetails 28. Dovetail28 and mating groove 30 can take any shape which allows removal ofpiston 29 lby a sliding motion transverse to the longitudinal axis ofpiston rod 26. For example, dovetail 28 can comprise a frustoconicalprotrusion on the end of rod 26 as shown, or can alternatively be heldon with a transverse wrist pin or other means. Pistons 29 can beprovided with a sealing device such as O-ring 31. A key 32 is iixed inend plates 11 and 12 so as to project into slot 27.

The pump of this invention can further be provided with an indicatorassembly including a driven spur gear 33, a shaft 34 threaded at itsouter end, an outboard shaft bearing 35, and an indicator pointer 36having a longitudinal internal threaded bore corresponding to thethreads on shaft 34 and a longitudinal key slot on its upper surfaceengaging an indicator bar 37. Bar 37 is fastened at its inboard end tothe pump housing, and shaft 34 is further supported by a bearing, notshown, in end plate 12.

Operation of the metering pump is now described. A suitable power sourceSuch as an electric motor 38, preferably of variable speed, is connectedas by a chain drive 39 to gear 21. The drive preferably enters the pumpcasing through cover plate 13. Energizing the power source causesrotation of driver assembly 19 including gears 2.1 and 22. Rotation ofdriver assembly 19 causes, by virtue of key slot 27, key 32, and threads20, a longitudinal movernent of piston rod 26 either to the left or tothe right, depending on the hand of threads 20 and the direction ofrotation of assembly 19. Movement of rod 26 causes correspondingmovement of pistons 29 linked directly thereto. Assuming the movement tobe to the right, fluid is drawn into the left cylinder by way of nipple18 on the left end, and other uid in the right cylinder which has beendrawn in on a previous cycle is now expelled via a nipple 18 on theright cylinder, which is not shown in the drawing. Drive gear 22 causesgear 23 to rotate in the opposite direction, which turns shaft 34. Thethreads on shaft 34 then move indicator 36 along bar 37, which can becalibrated in any desired manner. The threads of shaft 34 and of rod 26are preferably of a related pitch per inch but opposite hand, so thatindicator 36 can be positioned directly over the face of piston 29 andwill always indicate the location of the piston. A similar indicator canbe used in conjunction with each piston, but is shown here only over theright piston.

Indicator 36 can also be used as a novel control for the pump asfollows: Position sensing switches, such as microswitches 40a and 40h,can be mounted in a slideable or fixed position on bar 37 so as to beactuated by indicator 36. Actuation of a switch 40` can then be causedthrough suitable relays 44, to reverse direction of the pump drivemotor. Thus, when the piston 29 reaches one end of its stroke, one ofthe switches 40 on bar 37 will be actuated to cause the pump to reverseits travel direction. These same microswitches can also be used toactuate solenoid valves 41 and 42 on the pump inlet and discharge linesconnected to nipples 18. One useful way of connecting such inlet anddischarge lines is to connect a T -43 to each of the two nipples 18. Onearm of each of the two Ts is connected through, e.g., a solenoid valve41 to a source of the uid being pumped, and serves as the pump inlet orsuction. The remaining arm of each of the two Ts i-s connected through asimilar valve 42 to the fluid receptacle or point of iiuid use, andserves as a pump discharge. As mentioned, the solenoid valves in thepump suction and discharge lines can be actuated by microswitches 40 onbar 37 sensing the desired point of ending a pump stroke as reflected byindicator 36.

It will be obvious that a pump according to the present invention can bebuilt with only one piston and cylinder, although a double-acting pumpas shown in the drawing is preferred. It is also obvious that each ofthe two cylinders can be used on separate duty, i.e., the two cylinderscan be piped independently so as to handle a different fluid in eachcylinder.

An important feature of the present pump resides in its extremeflexibility as to the nature and pumping rate of fluids `which it iscapable of handling. Cylinder wall 16 can be fabricated from a widevariety of materials, and can include a sleeve liner of such as glass,Teflon, ceramic, polyethylene, etc. Piston 29 and plug 17 can besimilarly treated. Piston 29 can be slideably sealed to the interior ofcylinder wall 16 by lap fitting, an O-ring as shown, expandable pistonrings, etc. The volumetric capacity of this pump can be varied widely,and in several manners. First, the stroke-limiting microswitches can beslideably mounted on bar 37, and can be so positioned as to utilize anydesired fraction of the total potential pump stroke. Secondly, the pumpdrive motor speed can be varied so as to change the amount of timerequired per stroke. Thirdly, and perhaps most importantly, the pump isso designed that the entire cylinder assembly and piston can be quicklyand easily interchanged. The cylinders shown in the gure are of minimumcapacity in that their I.D. is just large enough to contain piston rod26. However, the pump capacity can be substantially increased quitequickly by simply unbolting ange from end plate 11 and/or 12,disconnecting the piping from nipple 18, sliding the cylinder off,replacing piston 29 with one of larger diameter by use of its dovetailor similar connection, and then installing a larger-bore cylinder by itsflange 15, and connecting the piping to the corresponding nipple 18.Indicator bar 37 can be provided, for instance, with spring clips at itsends to hold in place along its length replaceable scales calibrated tomatch the volumetric capacities of any number of cylinder and pistondiameters.

In certain instances, small amounts of the uid being handled will bewiped behind the piston into the interior of the pump casing. The pumpcan be provided with seals, not shown, to isolate such uid fromlubricant which can be provided in the bottom of the pump casing tolubricate the various gears therein. Suitable seal installations includemounting an annular seal on the inner face of end plates 11 and 12 so asto surround rod 26 and bear against the flat end surfaces of driverassembly 19; this is the preferred seal location, in that it permitsaccess of bearings 24 to lubricant in the pump casing sump. However,annular seals can alternatively be located so as to engage the outercylindrical surface of driver assembly 19- adjacent its ends, i.e.,between a spur gear 21 or 22 and the adjacent chamfer 23. In eitherevent, the small sub-chamber between such annular seal and thecorresponding inner face of the piston can be suitably drained or ventedto the exterior of the pump casing.

The pump of this invention is eminently suited for metering uid at afixed but readily changeable rate, such as a catalyst or reactantsolution or suspension to a chemical reactor. The pump can be used forproportioning uids by varying its drive motor speed responsive to therate of another uid, or by mechanically interconnecting, as by a chaindrive, two or more pumps of this invention having the same or differentcylinder diameters.

While the invention has been described in terms of certain embodimentsthereof, it is to be understood that it is not limited thereto andincludes a variety of operating conditions and means useful for carryingout the invention.

What is claimed is:

1. A reciprocal pump comprising a housing means, rotatable drive meanswithin said housing means, said rotatable drive means including aninternally threaded bore along the axis of rotation of said drive means,bearing means rotatably mounting said drive means within said housingmeans, externally threaded piston rod means extending through oppositewalls of said housing means and through and threadedly engaging saidthreaded bore, said piston rod means including a groove means in itsexternal surface substantially parallel to its longitudinal axis andfurther including piston-engaging means on one end, piston meansengageable with said piston-engaging means by motion substantiallytransverse to said longitudinal axis of said piston rod means, keyingmeans afxed to said housing means and engageable in said groove means,cylinder means extending beyond said piston means and including angemeans adjacent one end thereof, said ange means `being releasablyfastened to said housing means, and said cylinder means furtherincluding a closure means for and a fluid passage means adjacent the endof said cylinder means opposite said flange means, an indicator meanscomprising shaft means substantially parallel to the longitudinal axisof said piston rod means, said shaft means being threaded along at leasta portion of its length, means for imparting rotary motion to said shaftmeans in fixed proportion to rotation of said drive means, pointer meanshaving an internally threaded bore and adapted to traverse the threadedportion of said shaft, and means for preventing rotational movement andpermitting axial movement of said pointer means.

2. The pump of claim 1 further including T conduit means, one arm ofwhich communicates with said fluid passage means, a firstsolenoid-actuated valve means communicating with a second arm of said Tconduit means, a second solenoid-actuated valve means communicating withthe third arm of said T conduit means, a pair of position-sensing switchmeans responsive to movement of said pointer means, and means forclosing one of said solenoid-actuated valve means and opening the otherof said solenoid-actuated valve means upon actuation of one of said pairof switch means and for opening said one valve means and closing theother said valve means upon actuation of the other of said pair ofswitch means.

3. The pump of claim 2 further provided with power means for effectingrotation of said rotatable drive means, and means for reversing thedirection of said power means responsive to actuation of either one ofsaid pair of switch means.

References Cited UNITED STATES PATENTS 1,768,799 1/1930 Stanley 92-591,739,644 12/1929 Lugt 92--128 2,945,444 7/1960 Leissner V103--103,391,612 7/1968 Sneew 92-255 829,279 8/1906 Mears 92-33 1,233,8587/1917 Farmer 103-175 2,262,963 11/1941 Procissi 92-31 2,394,490 2/ 1946Schaeffer 74-57 2,471,596 5/ 1949 Williams 92-31 2,709,725 5/1955 Bieberet al. 74-57 3,065,704 11/1962 Hill 103-205 3,388,603 6/1968 Clark103-153 3,198,123 8/1965 Wilkinson et al 103-227 WILLIAM L. FREEH,Primary Examiner U.S. Cl. X.R.

